1. Field of the Invention
This invention concerns cushioning pads used in the field of health care to provide pressure reduction for the patient. The invention more particularly concerns cushion pads for patient care in wheelchairs, recliners, and other chairs used by patients in a health care environment.
2. Discussion of the Background
Previously existing cushioning pads have a number of shortcomings which can result in patient discomfort, and in a prolonged recovery period for the patient. Ideally, cushioning pads provide the lowest possible pressure on the supported surface of the patient and are able to substantially eliminate the pressure on the supported surface at selected locations on the patient.
One prior art device (Jacobson et al., U.S. Pat. No. 4,688,283) is constructed of a plurality of airtight air bladders each filled with foam material. Each air bladder is in contact with adjacent air bladders. The characteristic of the foam material is such that if it is compressed it will expand on its own, thus filling the bladder with air. Each air bladder has a valve connected to it, to individually regulate the amount of air that can flow into the air bladder. However, it produces an abrupt transition zone between an air bladder that is fully pressurized and an adjacent one that is completely evacuated, which creates patient discomfort.
Another prior art construction (Williams, U.S. Pat. No. 3,600,727) is similar to the prior art construction discussed above, but instead being filled with air, the air bladder is filled with a liquid. The bladders filled with a liquid tend to conduct body heat away from the patient which reduces blood flow and hence reduces the ability of the body to heal itself. Furthermore, this prior art construction contains all the disadvantages of the device described above, namely that the patient experiences discomfort due to the abrupt transition zone between pressurized and unpressurized fluid bladders.
Another prior art construction (Navach et al., U.S. Pat. No. 5,163,737) consists of a seat cushion and a backrest cushion. The seat cushion portion consists of a plurality of airtight, air bladders filled with a foam material. Adjacent air bladders are not in contact with each other. The air bladders are covered with a flexible polymer upholstery layer. Additionally this prior art construction contains an air valve for each air bladder to restrict the flow of air into and out of its respective air bladder. However, this prior art construction requires the use of an external pump or compressor to fill air bladders with air.
Thus, there is a need for a simple to use cushioning device that applies a substantially uniform pressure to the patient and which can selectively reduce the pressure at a point on the patient's body.